Aspects of the present disclosure relate to generating images using radar (reflection) tomography, and more particularly to a method, system and computer program product for generating images from return or backscattered radar signals and using radar tomography and Doppler-based projections.
Obtaining a high resolution image of a target area is desirable under certain circumstances or situations, such as surveillance, detecting unauthorized entry in an area, monitoring changes, locating a particular object or similar circumstance. Images generated by standard photographic techniques may be inadequate or not possible because environmental conditions or other conditions obscuring the target area. Additionally, only a two dimensional image can be obtained using standard photographic or imaging techniques.
Radar tomography is a technique for generating three-dimensional images using radar signals; however, radar tomography is also not without certain limitations. For example, a three-dimensional image may be generated or reconstructed at low operating frequencies suitable for penetrating intervening dielectric media, such as foliage or other intervening or obstructing material but a well behaved point spread function is required to provide a quality image. By well behaved point spread function, the response needs to have sufficient resolution and a side lobe pattern which minimizes the contribution of the response at other spatial positions. This is analogous to crosstalk or mutual interference. The response should also minimize contributions due to scattering objects that are outside or beyond the scene area to be imaged so that the image reconstruction can best reproduce the imaged object. Standard tomographic techniques or devices may achieve this by radiating or transmitting a waveform with a high bandwidth while collecting backscattered or return signals using a three-dimensional tomographic aperture. High bandwidth in the context of radar bandwidths may be approximately 10%-15% of the carrier frequency, or more. At low frequencies associated with good penetration of intervening dielectric media, there is insufficient (and shrinking) spectrum, limiting the bandwidth available. Additionally, wideband, low frequency antennas are physically large and ill-suited for integration with small airborne platforms, such as an unmanned aerial vehicles (UAV), usually used for surveillance and other purposes.